1. Field of the Invention
The invention is directed systems and methods of delivering medication to a patient's ear. Specifically, the invention is directed to systems and methods of non-invasively delivering medication to the inner ear.
2. Background of the Invention
The human ear has three main sections, which consist of the outer ear, the middle ear, and the inner ear. Sound waves enter the outer ear and travel through the ear canal to the middle ear. The ear canal channels the waves to the eardrum (or tympanic membrane), a thin, sensitive membrane stretched tightly over the entrance to the middle ear. The waves cause the eardrum to vibrate, which in turn passes the vibrations on to the hammer, one of three tiny bones in the ear. The hammer vibrating causes the anvil, the small bone touching the hammer, to vibrate. The anvil passes these vibrations to the stirrup, another small bone which touches the anvil. From the stirrup, the vibrations pass into the inner ear. The stirrup touches a liquid filled sack and the vibrations travel into the cochlea, which is shaped like a shell. Inside the cochlea, there are hundreds of special cells, called stereocilia, attached to nerve fibers, which can transmit information to the brain. The brain processes the information from the ear. FIG. 1 depicts a basic diagram of the human ear.
As acoustic sensors in mammals, stereocilia are lined up in the Organ of Corti within the cochlea of the inner ear. In hearing, stereocilia transform the mechanical energy of sound waves into electrical signals for the hair cells, which ultimately leads to an excitation of the auditory nerve. Stereocilia are composed of cytoplasm with embedded bundles of cross-linked actin filaments. The actin filaments anchor to the terminal web and the top of the cell membrane and are arranged in grade of height. When the stapes (the stirrup-shaped bone in the inner ear) causes sound waves in the endolymphatic fluid in the cochlea, the stereocilia are deflected in a shearing motion, which results in electrical signal for the hair cell.
In the inner ear, stereocilia are the mechanosensing organelles (structures with specialized functions, suspended in the cytoplasm of a cell) of hair cells, which respond to fluid motion in numerous types of animals for various functions, including hearing and balance. They are about 10-50 micrometers in length and share some similar features of microvilli. The hair cells turn the fluid pressure and other mechanical stimuli into electric stimuli via the many microvilli that make up stereocilia rods. Stereocilia exist in the auditory and vestibular systems.
Auditory dysfunctions are common. Various situations or medical conditions of the inner ear require the administration of drugs or like medicines to the middle ear. Such medical conditions or inner ear disorders can include sudden neurosensory hearing loss, Meniere's disease, and tinnitus. For example, in the United States, the prevalence of tinnitus when the whole population is considered is approximately 3%. This prevalence is only 1% under the age of 45 but increases significantly with age, rising to 9% in the population over 65 years. Tinnitus is a noise in the ears, often described as ringing, buzzing, roaring, or clicking. Subjective and objective forms of tinnitus exist, with objective tinnitus often caused by muscle contractions or other internal noise sources in the area proximal to auditory structures. In certain cases, external observers can hear the sound generated by the internal source of objective tinnitus. In subjective forms, tinnitus is audible only to the subject. Tinnitus varies in perceived amplitude, with some subjects reporting barely audible forms and others essentially deaf to external sounds and/or incapacitated by the intensity of the perceived noise. It has also been reported that, although the deaf cannot hear, they can experience tinnitus.
Typical devices for providing treatment to inner ear afflictions are implanted in the body and have a reservoir of medication that is dispensed into the inner ear to treat the symptoms. These devices are highly invasive, require surgery to implant, and then must be removed via surgery once the treatment is over. The invasive nature of the devices leads to the increased possibility of infection or that the patient's body may reject the device. Therefore, it is desirable to have a non-invasive device for treating inner ear conditions.